libvorbis release checklist.

- Bump vendor string for encoder changes in lib/info.c
- Bump release version and sonames in configure.ac
- Update CHANGES.
- Update overall copyright dates on COPYING and README.
- Verify 'make distcheck' works.
- Verify everything is committed.
- Tag release:
  svn cp https://svn.xiph.org/trunk/vorbis https://svn.xiph.org/tags/vorbis/libvorbis-x.y.z
- Copy source packages to a checkout of https://svn.xiph.org/releases/vorbis/
- Add them to the repo and update checksum files there.
- Update https://xiph.org/downloads/
- Update topic in the #vorbis irc channel on freenode.net.
- Post announcement to https://xiph.org/press/ and link from front page.
- Announce new release to mailing list.
